Polymerization catalysts

ABSTRACT

A catalyst for the polymerization of 1-olefins is disclosed, which comprises (1) a compound of Formula B wherein M is Fe[II], Fe[III], Co[I], Co[II], Co[III], Mn[I], Mn[II], Mn[III], Mn[IV], Ru[II], Ru[III] or Ru[IV]; X represents an atom or group covalently or ionically bonded to the transition metal M; T is the oxidation state of the transition metal M and b is the valency of the atom or group X; R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  are independently selected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl or substituted heterohydrocarbyl; and when any two or more of R 1 –R 7  are hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl or substituted heterohydrocarbyl, said two or more can be linked to form one or more cyclic substituents; and (2) a further catalyst. Copolymers made using the catalyst having specific physical properties are also disclosed

This application is a divisional of application Ser. No. 09/659,589,filed Sep. 11, 2000, now U.S. Pat. No. 6,657,026, which is acontinuation of International application PCT/GB 99/00714, filed Mar.10, 1999, both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to novel transition metal compounds and totheir use as polymerisation catalysts.

The use of certain transition metal compounds to polymerise 1-olefins,for example, ethylene, is well established in the prior art. The use ofZiegler-Natta catalysts, for example, those catalysts produced byactivating titanium halides with organometallic compounds such astriethylaluminium, is fundamental to many commercial processes formanufacturing polyolefins. Over the last twenty or thirty years,advances in the technology have led to the development of Ziegler-Nattacatalysts which have such high activities that that olefin polymers andcopolymers containing very low concentrations of residual catalyst canbe produced directly in commercial polymerisation processes. Thequantities of residual catalyst remaining in the produced polymer are sosmall as to render unnecessary their separation and removal for mostcommercial applications. Such processes can be operated by polymerisingthe monomers in the gas phase, or in solution or in suspension in aliquid hydrocarbon diluent. Polymerisation of the monomers can becarried out in the gas phase (the “gas phase process”), for example byfluidising under polymerisation conditions a bed comprising the targetpolyolefin powder and particles of the desired catalyst using afluidising gas stream comprising the gaseous monomer. In the so-called“solution process” the (co)polymerisation is conducted by introducingthe monomer into a solution or suspension of the catalyst in a liquidhydrocarbon diluent under conditions of temperature and pressure suchthat the produced polyolefin forms as a solution in the hydrocarbondiluent. In the “slurry process” the temperature, pressure and choice ofdiluent are such that the produced polymer forms as a suspension in theliquid hydrocarbon diluent. These processes are generally operated atrelatively low pressures (for example 10–50 bar) and low temperature(for example 50 to 150° C.).

Commodity polyethylenes are commercially produced in a variety ofdifferent types and grades. Homopolymerisation of ethylene withtransition metal based catalysts leads to the production of so-called“high density” grades of polyethylene. These polymers have relativelyhigh stiffness and are useful for making articles where inherentrigidity is required. Copolymerisation of ethylene with higher 1-olefins(e.g. butene, hexene or octene) is employed commercially to provide awide variety of copolymers differing in density and in other importantphysical properties. Particularly important copolymers made bycopolymerising ethylene with higher 1-olefins using transition metalbased catalysts are the copolymers having a density in the range of 0.91to 0.93. These copolymers which are generally referred to in the art as“linear low density polyethylene” are in many respects similar to the socalled “low density” polyethylene produced by the high pressure freeradical catalysed polymerisation of ethylene. Such polymers andcopolymers are used extensively in the manufacture of flexible blownfilm.

An important feature of the microstructure of the copolymers of ethyleneand higher 1-olefins is the manner in which polymerised comonomer unitsare distributed along the “backbone” chain of polymerised ethyleneunits. The conventional Ziegler-Natta catalysts have tended to producecopolymers wherein the polymerised comonomer units are clumped togetheralong the chain. To achieve especially desirable film properties fromsuch copolymers the comonomer units in each copolymer molecule arepreferably not clumped together, but are well spaced along the length ofeach linear polyethylene chain. In recent years the use of certainmetallocene catalysts (for examplebiscyclopentadienylzirconiumdichloride activated with alumoxane) hasprovided catalysts with potentially high activity and capable ofproviding an improved distribution of the comonomer units. However,metallocene catalysts of this type suffer from a number ofdisadvantages, for example, high sensitivity to impurities when usedwith commercially available monomers, diluents and process gas streams,the need to use large quantities of expensive alumoxanes to achieve highactivity, and difficulties in putting the catalyst on to a suitablesupport.

WO98/27124, published after the earliest priority date of thisinvention, discloses that ethylene may be polymerised by contacting itwith certain iron or cobalt complexes of selected2,6-pyridinecarboxaldehydebis(imines) and 2,6-diacylpyridinebisimines);and our own copending application GB 9718775.1 has disclosedpolymerisation catalysts containing novel nitrogen-containing transitionmetal compounds which comprise the skeletal unit depicted in Formula B:

wherein M is Fe[II], Fe[III], Co[I], Co[II], Co[III], Mn[I], Mn[II],Mn[III], Mn[IV], Ru[II], Ru[III] or Ru[IV]; X represents an atom orgroup covalently or ionically bonded to the transition metal M; T is theoxidation state of the transition metal M and b is the valency of theatom or group X; R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are independentlyselected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl; and when any two ormore of R¹–R⁷ are hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl, said two or more canbe linked to form one or more cyclic substituents.

An object of the present invention is to provide a novel catalyst systemsuitable for polymerising monomers, for example, olefins, and especiallyfor polymerising ethylene alone or for copolymerising ethylene withhigher 1-olefins. A further object of the invention is to provide animproved process for the polymerisation of olefins, especially ofethylene alone or the copolymerisation of ethylene with higher 1-olefinsto provide homopolymers and copolymers having controllable molecularweights.

SUMMARY OF THE INVENTION

We have unexpectedly discovered that the combination of catalysts of theFormula B with other catalysts can produce a highly active catalyticsystem in which the resultant polymers exhibit improved performance andprocessing properties.

The present invention provides a polymerisation catalyst comprising (1)a compound of the Formula B:

wherein M is Fe[II], Fe[III], Co[I], Co[II], Co[III], Mn[I], Mn[II],Mn[III], Mn[IV], Ru[II], Ru[III] or Ru[IV]; X represents an atom orgroup covalently or ionically bonded to the transition metal M; T is theoxidation state of the transition metal M and b is the valency of theatom or group X; R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are independentlyselected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl; and when any two ormore of R¹–R⁷ are hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl, said two or more canbe linked to form one or more cyclic substituents; and (2) a furthercatalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a plot of secant modules (MPa) versus comonomer content trend;and

FIG. 2 is a plot of complex viscosity versus frequency (rad/s).

DETAILED DESCRIPTION OF THE INVENTION

The catalysts (1) and (2) can if desired both be a transition metalcompound of Formula B. The catalyst may comprise, for example, a mixtureof 2,6-diacetylpyridinebis(2,6-diisopropylanil)FeCl₂ complex and2,6-diacetylpyridinebis(2,4,6-trimethylanil)FeCl₂ complex, or a mixtureof 2,6-diacetylpyridine(2,6-disopropylanil)CoCl₂ and2,6-diacetylpyridinebis(2,4,6-trimethylanil)FeCl₂. However preferablythe further catalyst (2) is not covered by the definition of (1).

The further catalyst (2) may be for example, a Ziegler Natta catalyst, aPhillips type (chromium oxide) catalyst or a metallocene catalyst. Othercatalysts (2) include monocyclopentadienyl constrained geometry typecatalysts and bidentate α-diimine late transition metal catalysts.Metallocenes may typically be represented by the general formula:(C₅R_(n))_(y)Z_(x)(C₅R_(m))ML_((4−y−1))where

-   -   (C₅R_(x))_(n) and (C₅R_(m)) are cyclopentadienyl ligands,    -   R is hydrogen, alkyl, aryl, alkenyl, etc.    -   M is a Group IVA metal    -   Z is a bridging group,    -   L is an anionic ligand, and    -   y is 0, 1 or 2, n and m are 1–5, x is 0 or 1.        The most preferred complexes are those wherein y is 1 and L is        halide or alkyl. Typical examples of such complexes are        bis(cyclopentadienyl)zirconium dichloride and        bis(cyclopentadienyl zirconium dimethyl. In such metallocene        complexes the cyclopentadienyl ligands may suitably be        substituted by alkyl groups such as methyl, n-butyl or vinyl.        Alternatively the R groups may be joined together to form a ring        substituent, for example indenyl or fluorenyl. The        cyclopentadienyl ligands may be the same or different. Typical        examples of such complexes are bis(n-butylcyclopentadienyl)        zirconium dichloride or bis (methylcyclopentadienyl)zirconium        dichloride.

Examples of monocyclopentadienyl- or constrained geometry complexes maybe found in EP 416815A, EP 420436A, EP 418044A and EP 491842A thedisclosures of which are incorporated herein by reference. A typicalexample of such a moncyclopentadienyl complex is(tert-butylamido)(tetramethyl cyclopentadienyl) dimethyl silanetitaniumdimethyl.

Further examples of metallocene complexes are those wherein the anionicligand represented in the above formula is replaced with a diene moiety.In such complexes the transition metal may be in the +2 or +4 oxidationstate and a typical example of this type of complex is ethylene bisindenyl zirconium (II) 1,4-diphenyl butadiene. Examples of suchcomplexes may be found in EP 775148A the disclosure of which isincorporated herein by reference.

Monocyclopentadienyl complexes having diene moieties have also been usedfor the polymerisation of olefins. Such complexes may be exemplified by(tert-butylamido)(tetramethylcyclopentadienyl) dimethylsilanetitanium(II) penta-1,3-diene. Such complexes are described in EP 705269A thedisclosure of which is incorporated herein by reference.

Other transition metal complexes which may comprise catalyst (2) aboveare complexes having hetero ring ligands attached to the transitionmetal, for example O, NR or S ligands. Such complexes are disclosed forexample in EP 735057A and may be illustrated by indenyl zirconiumtris(diethylcarbamate).

The further catalyst (2) preferably comprises a heterogeneous catalystor a supported catalyst which provides a support for the catalyst (1).It is preferred that the catalyst additionally incorporates (3) anactivating quantity of an activator compound comprising a Lewis acidcapable of activating the catalyst for olefin polymerisation, preferablyan organoaluminium compound or a hydrocarbylboron compound.

The activator compound for the catalysts of the present invention issuitably selected from organoaluminium compounds and hydrocarbylboroncompounds. Suitable organoaluminium compounds include trialkyaluminiumcompounds, for example, trimethylaluminium, triethylaluminium,tributylaluminium, tri-n-octylaluminium, ethylaluminium dichloride,diethylaluminium chloride and alumoxanes. Alumoxanes are well known inthe art as typically the oligomeric compounds which can be prepared bythe controlled addition of water to an alkylaluminium compound, forexample trimethylaluminum. Such compounds can be linear, cyclic ormixtures thereof. Commercially available alumoxanes are generallybelieved to be mixtures of linear and cyclic compounds. The cyclicalumoxanes can be represented by the formula [R¹⁶AlO], and the linearalumoxanes by the formula R¹⁷(R¹⁸AlO), wherein s is a number from about2 to 50, and wherein R¹⁶, R¹⁷, and R¹⁸ represent hydrocarbyl groups,preferably C₁ to C₆ alkyl groups, for example methyl, ethyl or butylgroups.

Examples of suitable hydrocarbylboron compounds aredimethylphenylammoniumtetra(phenyl)borate, trityltetra(phenyl)borate,triphenylboron, dimethylphenylammonium tetra(pentafluorophenyl)borate,sodium tetrakis[(bis-3,5-trifluoromethyl)phenyl]borate,H⁺(OEt₂)[(bis-3,5-trifluoromethyl)phenyl]borate,trityltetra(pentafluorophenyl)borate and tris(pentafluorophenyl)boron.

In the preparation of the catalysts of the present invention thequantity of activating compound selected from organoaluminium compoundsand hydrocarbylboron compounds to be employed is easily determined bysimple testing, for example, by the preparation of small test sampleswhich can be used to polymerise small quantities of the monomer(s) andthus to determine the activity of the produced catalyst. It is generallyfound that the quantity employed is sufficient to provide 0.1 to 20,000atoms, preferably 1 to 2000 atoms of aluminium or boron per Fe, Co, Mnor Ru metal atom in the compound of Formula A

In a preferred embodiment, the catalyst (1) is supported on aheterogeneous catalyst as catalyst (2), for example, a magnesium halidesupported Ziegler Natta catalyst, a Phillips type (chromium oxide)supported catalyst or a supported metallocene catalyst. Formation of thesupported catalyst can be achieved for example by treating thetransition metal compounds of the present invention with alumoxane in asuitable inert diluent, for example a volatile hydrocarbon, slurrying aparticulate support material with the product and evaporating thevolatile diluent. The quantity of support material employed can varywidely, for example from 100,000 to 1 grams per gram of metal present inthe transition metal compound. A particularly preferred support is aZiegler Natta catalyst.

In a further aspect of the present invention compound (1) comprises theskeletal unit depicted in Formula Z:

wherein M is Fe[II], Fe[III], Co[I], Co[II], Co[III], Mn[I], Mn[II],Mn[III], Mn[IV], Ru[II], Ru[III] or Ru[IV]; X represents an atom orgroup covalently or ionically bonded to the transition metal M; T is theoxidation state of the transition metal M and b is the valency of theatom or group X; R¹ to R⁴, R⁶ and R¹⁹ to R²⁸ are independently selectedfrom hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl; when any two or moreof R¹ to R⁴, R⁶ and R¹⁹ to R²⁸ are hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl, said two or more canbe linked to form one or more cyclic substituents; with the proviso thatat least one of R¹⁹, R²⁰, R²¹ and R²² is hydrocarbyl, substitutedhydrocarbyl, heterohydrocarbyl or substituted heterohydrocarbyl whenneither of the ring systems P and Q forms part of a polyaromaticfused-ring system. In this particular aspect of the present invention,in the case that neither of the ring systems P and Q forms part of apolyaromatic ring system, it is preferred that at least one of R¹⁹ andR²⁰, and at least one of R²¹ and R²² is selected from hydrocarbyl,substituted hydrocarbyl, heterohydrocarbyl or substitutedheterohydrocarbyl, and most preferably each of R¹⁹, R²⁰, R²¹ and R²² isselected from hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl orsubstituted heterohydrocarbyl.

In a further aspect of the present invention compound (1) comprises theskeletal unit depicted in Formula Z:

wherein M is Fe[II], Fe[III], Co[I], Co[II], Co[III], Mn[I], Mn[II],Mn[III], Mn[IV], Ru[II], Ru[III] or Ru[IV]; X represents an atom orgroup covalently or ionically bonded to the transition metal M; T is theoxidation state of the transition metal M and b is the valency of theatom or group X; R¹ to R⁴, R⁶ and R¹⁹ to R²⁰ are independently selectedfrom hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl; when any two or moreof R¹ to R⁴, R⁶ and R¹⁹ to R²⁸ are hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl, said two or more canbe linked to form one or more cyclic substituents; with the proviso thatR¹⁹, R²⁰, R²¹ and R²² are hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl when neither of thering systems P and Q forms part of a polyaromatic fused-ring system.

Subject to the foregoing provisos regarding R¹⁹, R²⁰, R²¹ and R²² inFormula Z, R¹ to R⁴, R⁶ and R¹⁹ to R²⁸′ in the compounds depicted inFormulae B and Z of the present invention are preferably independentlyselected from hydrogen and C₁, to C₈ hydrocarbyl, for example, methyl,ethyl, n-propyl, n-butyl, n-hexyl, and n-octyl. In Formula B, R⁵ and R⁷are preferably independently selected from substituted or unsubstitutedalicyclic, heterocyclic or aromatic groups, for example, phenyl,1-naphthyl, 2-naphthyl, 2-methylphenyl, 2-ethylphenyl,2,6-diisopropylphenyl, 2,3-diisopropylphenyl, 2,4-diisopropylphenyl,2,6-di-n-butylphenyl, 2,6-dimethylphenyl, 2,3-dimethylphenyl,2,4-dimethylphenyl, 2-t-butylphenyl, 2,6-diphenylphenyl,2,4,6-trimethylphenyl, 2,6-trifluoromethylphenyl,4-bromo-2,6-dimethylphenyl, 3,5 dichloro2,6-diethylphenyl, and2,6,bis(2,6-dimethylphenyl)phenyl, cyclohexyl and pyridinyl.

The ring systems P and Q in Formula Z are preferably independently2,6-hydrocarbylphenyl or fused-ring polyaromatic, for example,1-naphthyl, 2-naphthyl, 1-phenanthrenyl and 8-quinolinyl.

In yet a further aspect of the present invention, compound (1) comprisesthe skeletal unit depicted in Formula T:

wherein M is Fe[II], Fe[III], Co[I], Co[II], Co[III], Mn[I], Mn[II],Mn[III], Mn[IV], Ru[II], Ru[III] or Ru[IV]; X represents an atom orgroup covalently or ionically bonded to the transition metal M; T is theoxidation state of the transition metal M and b is the valency of theatom or group X; R¹ to R⁴, R⁶ and R²⁹ to R³² are independently selectedfrom hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl; when any two or moreof R¹ to R⁴, R⁶ and R²⁹ to R³² are hydrocarbyl, substituted hydrocarbyl,heterohydrocarbyl or substituted heterohydrocarbyl, said two or more canbe linked to form one or more cyclic substituents

In the compound of Formula B of the present invention, M is preferablyFe[II]. In the compounds of Formula Z or Formula T of the presentinvention, M is preferably Fe[II], Mn[II] or Co[III].

Examples of the atom or group X in the compounds of Formula B, Z and Tare halide, for example, chloride, bromide; iodide; hydride;hydrocarbyloxide, for example, methoxide, ethoxide, isopropoxide,phenoxide; carboxylate, for example, formate, acetate, benzoate;hydrocarbyl, for example, methyl, ethyl, propyl, butyl, octyl, decyl,phenyl, benzyl; substituted hydrocarbyl; heterohydrocarbyl; tosylate;and triflate. Preferably X is selected from halide, hydride andhydrocarbyl. Chloride is particularly preferred.

A particularly preferred embodiment of the present invention comprises apolymerisation catalyst comprising (1) as the transition metal compound,the Formula B or Formula Z or Formula T compound, (2) a further catalyst(preferably not covered by the definition of (1)), and preferably also(3) an activating quantity of an activator compound comprising a Lewisacid capable of activating the catalyst for olefin polymerisation,preferably an organoaluminium compound or a hydrocarbylboron compound.When catalyst (2) is a Ziegler-Natta catalyst, then it is preferred thatcomponents (1) and (3) are premixed prior to addition to (2).

In a further aspect of the present invention the polymerisation catalystsystem additionally comprises (4) a neutral Lewis base.

In this further aspect of the present invention, the transition metalcompound is preferably of Formula B, Z or T. The iron and cobaltcompounds are preferred. The preferences in relation to the activatorcompound are the same as expressed above in relation to the catalysts ofthe present invention. Neutral Lewis bases are well known in the art ofZiegler-Natta catalyst polymerisation technology. Examples of classes ofneutral Lewis bases suitably employed in the present invention areunsaturated hydrocarbons, for example, alkenes or alkynes, primary,secondary and tertiary amines, amides, phosphoramides, phosphines,phosphites, ethers, thioethers, nitriles, carbonyl compounds, forexample, esters, ketones, aldehydes, carbon monoxide and carbon dioxide,sulphoxides, sulphones and boroxines. Although 1-olefins are capable ofacting as neutral Lewis bases, for the purposes of the present inventionthey are regarded as monomer or comonomer 1-olefins and not as neutralLewis bases per se. However, alkenes which are internal olefins, forexample, 2-butene and cyclohexene are regarded as neutral Lewis bases inthe present invention. Preferred Lewis bases are tertiary amines andaromatic esters, for example, dimethylaniline, diethylaniline,tributylamine, ethylbenzoate and benzylbenzoate. In this particularaspect of the present invention, components (1), (2), (3) and (4) of thecatalyst system can be brought together simultaneously or in any desiredorder. However, if components (3) and (4) are compounds which interacttogether strongly, for example, form a stable compound together, it ispreferred to bring together either components (1), (2) and (3) orcomponents (1), (2) and (4) in an initial step before introducing thefinal defined component. Preferably components (1), (2) and (4) arecontacted together before component (3) is introduced. The quantities ofcomponents (1), (2) and (3) employed in the preparation of this catalystsystem are suitably as described above in relation to the catalysts ofthe present invention. The quantity of the neutral Lewis Base (component(4)) is preferably such as to provide a ratio of component (1)+(2):component (4) in the range 100:1 to 1:1000, most preferably in the range1:1 to 1:20. Components (1), (2) and (4) of the catalyst system can bebrought together, for example, as the neat materials, as a suspension orsolution of the materials in a suitable diluent or solvent (for examplea liquid hydrocarbon), or, if at least one of the components isvolatile, by utilising the vapour of that component. The components canbe brought together at any desired temperature. Mixing the componentstogether at room temperature is generally satisfactory. Heating tohigher temperatures e.g. up to 120° C. can be carried out if desired,e.g. to achieve better mixing of the components. It is preferred tocarry out the bringing together of components (1), (2) and (4) in aninert atmosphere (eg dry nitrogen) or in vacuo. If it is desired to usethe catalyst on a support material (see below), this can be achieved,for example, by preforming the catalyst system comprising components(1), (2), (3) and (4) and impregnating the support material preferablywith a solution thereof, or by introducing to the support material oneor more of the components simultaneously or sequentially. If desired thesupport material itself can have the properties of a neutral Lewis baseand can be employed as, or in place of, component (4). An example of asupport material having neutral Lewis base properties ispoly(aminostyrene) or a copolymer of styrene and aminostyrene (ievinylaniline). In an alternative preferred embodiment, components (2)and (3) are mixed together prior to the addition of component (1). Thisis particularly preferred when catalyst (2) is itself the support, suchthat catalyst (1) and the activator (3) are added separately to thesupport. In a further alternative catalyst (2) and activator (3) areadded separately to catalyst (1).

The following are examples of nitrogen-containing transition metalcomplexes (1):

-   2,6-diacetylpyridinebis(2,6-diisopropylanil)FeCl₂-   2,6-diacetylpyridine(2,6-disopropylanil)MnCl₂-   2,6-diacetylpyridine(2,6-diisopropylanil)CoCl₂-   2,6-diacetylpyridinebis(2-tert.-butylanil)FeCl₂-   2,6-diacetylpyridinebis(2,3-dimethylanil)FeCl₂-   2,6-diacetylpyridinebis(2-methylanil)FeCl₂-   2,6-diacetylpyridinebis(2,4-dimethylanil)FeCl₂-   2,6-diacetylpyridinebis(2,6-dimethylanil)FeCl₂-   2,6-diacetylpyridinebis(2,6-dimethylanil)FeCl₂-   2,6-dialdiminepyridinebis(2,4,6-trimethylanil)FeCl₂-   2,6-dialdiminepyridinebis(2,6-diethylanil)FeCl₂-   2,6-dialdiminepyridinebis(2,6-diisopropylanil)FeCl₂-   2,6-dialdiminepyridinebis(1-naphthil)FeCl₂ and-   2,6-bis(1,1-diphenylhydrazone)pyridine.FeCl₂.

The present invention further provides a process for the polymerisationor copolymerisation of 1-olefins, comprising contacting the monomericolefin(s) under polymerisation conditions with a polymerisation catalystcomprising (1) a compound based on the Formula B, T or Z, and (2) afurther catalyst. The further catalyst (2) is preferably not covered bythe above definition (1). In a preferred process the catalystadditionally comprises an activating quantity of an activator compoundcomprising a Lewis acid capable of activating the catalyst for olefinpolymerisation, preferably an organoaluminium compound or ahydrocarbylboron compound. The process of the invention may alsocomprise the additional step of blowing the resultant polymer into afilm.

The catalysts (1) and (2) may be contacted with the olefin to bepolymerised in the form of a single catalyst system, or they may beadded to the reactor separately.

The process/catalyst of the invention is especially useful forcopolymerising ethylene with other 1-olefins One disadvantage of thecatalysts disclosed in GB 9718775.1 A, where the only catalyst in thesystem is catalyst (1) as defined in this invention, is that theyproduce copolymers having only a relatively low level of comonomerincorporation for a given level of comonomer in the reaction vessel. Wehave discovered that the catalyst system of the present invention canproduce copolymers having significantly higher levels of comonomerincorporation for the same level of comonomer reactant. Thus in apreferred process for the copolymerisation of ethylene and a further1-olefin, particularly a 1-olefin having 6 or more carbon atoms, thedegree of short chain branching per thousand carbons (SCB) in theresultant copolymer is greater than zero and also equal to or greaterthan 18.18R−0.16 where R is the ratio of partial pressure of further1-olefin to that of ethylene. Preferably the SCB is greater than orequal to 18.18R−0.05, more preferably 18.18R−0.04. A further aspect ofthe invention provides a copolymer of ethylene and a further 1-olefinhaving an SCB of 2.0, preferably 3.0 or greater and comprising residuesof a nitrogen-containing iron complex, wherein the iron concentration isfrom 0.01 to 1000 parts by weight per million parts of copolymer,preferably 0.01 to 10 ppm by weight, for example 0.11 to 1.03 ppm byweight.

The process of the invention also permits the short chain branching tobe preferentially located in a particular portion of the molecularweight distribution of the copolymer. Thus a further aspect of theinvention provides a method of selecting the portion of the molecularweight distribution of a copolymer of ethylene and a further 1-olefin inwhich units of said further 1-olefin are located, comprising contactingthe monomeric olefins under polymerisation conditions with apolymerisation catalyst comprising (1) a compound based on the FormulaB, T or Z, and (2) a further catalyst not covered by the abovedefinition (1). Preferably the 1-olefin has 6 or more carbon atoms. In apreferred method the portion of the molecular weight distribution of thecopolymer in which units of the further 1-olefin are located is withinthe 50% by weight of the copolymer having the highest molecular weight.A further aspect of the invention provides a copolymer of ethylene and afurther 1-olefin, particularly a 1-olefin having 6 or more carbon atoms,comprising residues of a nitrogen-containing iron complex wherein theiron concentration is from 0.01 to 10 parts by weight per million partsof copolymer, and in which at least 50%, preferably at least 60% andmore preferably at least 70% of the short chain branching is locatedwithin the 50% by weight of the copolymer having the highest molecularweight. Generally it is preferred that at least 80% of the short chainbranching is located within the 80% by weight of the copolymer havingthe highest molecular weight.

Copolymerisation permits the control of physical properties of thepolymer such as density and environmental stress crack resistance;however it generally results in polymers having reduced modulus(rigidity). High modulus (or rigidity) is necessary for pipe andmoulding products where the ability to support hydrostatic loads isimportant, and in film applications where is reduces the degree of sagand misalignment which can occur during film production or handling. Theuse of the catalyst system of the present invention where theheterogeneous catalyst is a Ziegler-Natta catalyst is capable ofproducing copolymers having a higher modulus for a given comonomercontent than has hitherto been possible, and a better blend of physicalproperties such as those mentioned above.

Accordingly in a further aspect the present invention provides acopolymer of ethylene and a further 1-olefin wherein the degree of shortchain branching per thousand carbons (SCB) is from 2.0 to 10, and therelationship of modulus in MPa (M) to SCB (B) is defined by the equationM=k−62.5B where k is 820 or greater.

Whilst many copolymers are known having SCB greater than 2, theparticular combination of high SCB, which, for example, is desirable intough films, and high modulus has not hitherto been achievable. Thepreferred range of SCB is between 2 and 8, though more preferably SCB isgreater than 2.5, and most preferably greater than 3.0. The relationshipbetween modulus and SCB is preferably such that k is 830 or greater,more preferably 840 or greater, and particularly 850 or greater. Apreferred relationship is defined by the equation M=k−65.5B where k is850 or greater, a more preferred one by the equation M=k−67.5B where kis 870 or greater, and a particularly preferred one by the equationM=k−70.5B where k is 90or greater. Another preferred relationship isdefined by the equation M=k−60B where k is 815 or greater, a morepreferred one by the equation M=k−57.5B where k is 810 or greater, and aparticularly preferred one by the equation M=k−55B where k is 805 orgreater. In FIG. 1 a plot of modulus against SCB is shown, whichdemonstrates the region attainable by the invention but not by knowncopolymers. Points are shown on the graph not only for copolymersaccording to the invention, but also for known copolymers. The regioncovered by the invention is that on or above the diagonal line, andbetween SCB/1000C=2.0 and 10.

Preferred comonomers are olefins having from 4 to 8 carbons, such as1-butene, 1-hexene, 4-methylpentene-1, and octene.

The above copolymers are generally preferred to have high molecularweights for maximum impact performance. However the high viscosity ofsuch materials can create problems during processing, for example withfilm blowing, such as high stresses and energy consumption duringcompounding and processing, degradation of the polymer, unbalancedmachine direction and transverse direction tear strengths, and poordowngauging performance. This can make it difficult or impossible toproduce tough thin (10–15 micron) film. It is therefore necessary toensure that products suitable for film applications have a molecularweight distribution which lowers high shear (extrusion) viscosity whilemaintaining other desirable features. The copolymers of this aspect ofthe invention have rheology comparable to other commercially availableprocessable tough film grades (FIG. 2). The viscosity-shear ratedependence shown graphically in FIG. 2 can be modelled by the Carreauequation which extrapolates the curve to calculate the zero shear rateviscosity. Thus the copolymer of Example 32.5 has a rheology defined bythe equation η=(4.455×10⁶)[1+1.776χ^(0.1286)]^((−(0.070/0.1286)) where ηis viscosity at 180° C. and χ is the shear rate. The zero shearviscosity of the copolymer of Example 32.5 is therefore intermediatebetween that of the other two commercial grades. Copolymers of thisaspect of the invention are preferred to have a zero shear viscosity ofbetween 0.1×10⁶ Ps and 12×10⁶ Ps.

The polymers and copolymers of the invention are generally made in theform of a powder, the particle size of which may be from 0.1 to 18 mmdiameter. Pellets may also be made, having a diameter of 0.2 to 30 mm.

The polymerisation conditions employed in the process of the inventioncan be, for example, solution phase, slurry phase or gas phase. Ifdesired, the catalyst can be used to polymerise the olefin under highpressure/high temperature process conditions wherein the polymericmaterial forms as a melt in supercritical ethylene. Preferably thepolymerisation is conducted under gas phase fluidised bed conditions.Suitable monomers for use in the polymerisation process of the presentinvention are, for example, ethylene, propylene, butene, hexene, methylmethacrylate, methyl acrylate, butyl acrylate, acrylonitrile, vinylacetate, and styrene. Preferred monomers for homopolymerisationprocesses are ethylene and propylene.

Slurry phase polymerisation conditions or gas phase polymerisationconditions are particularly useful for the production of high densitygrades of polyethylene. In these processes the polymerisation conditionscan be batch, continuous or semi-continuous. In the slurry phase processand the gas phase process, the catalyst is generally fed to thepolymerisation zone in the form of a particulate solid. In the case ofcatalyst (1) (and also catalyst (2) if this too is a compound accordingto formula B), this solid may be an undiluted solid catalyst systemformed from a nitrogen-containing complex and an activator, or can bethe solid complex alone. In the latter situation, the activator can befed to the polymerisation zone, for example as a solution, separatelyfrom or together with the solid complex. Preferably the catalyst systemor the transition metal complex component of the catalyst systememployed in the slurry polymerisation and gas phase polymeriastion issupported on a support material. Most preferably the catalyst system issupported on a support material prior to its introduction into thepolymerisation zone. Suitable support materials are, for example,silica, alumina, zirconia, talc, kieselguhr, or magnesia. Impregnationof the support material can be carried out by conventional techniques,for example, by forming a solution or suspension of the catalystcomponents in a suitable diluent or solvent, and slurrying the supportmaterial therewith. The support material thus impregnated with catalystcan then be separated from the diluent for example, by filtration orevaporation techniques.

In the slurry phase polymerisation process the solid particles ofcatalyst, or supported catalyst, are fed to a polymerisation zone eitheras dry powder or as a slurry in the polymerisation diluent. Preferablythe particles are fed to a polymerisation zone as a suspension in thepolymerisation diluent. The polymerisation zone can be, for example, anautoclave or similar reaction vessel, or a continuous loop reactor, egof the type well-know in the manufacture of polyethylene by the PhillipsProcess. When the polymerisation process of the present invention iscarried out under slurry conditions the polymerisation is preferablycarried out at a temperature above 0° C., most preferably above 15° C.The polymerisation temperature is preferably maintained below thetemperature at which the polymer commences to soften or sinter in thepresence of the polymerisation diluent. If the temperature is allowed togo above the latter temperature, fouling of the reactor can occur.Adjustment of the polymerisation within these defined temperature rangescan provide a useful means of controlling the average molecular weightof the produced polymer. A further useful means of controlling themolecular weight is to conduct the polymerisation in the presence ofhydrogen gas which acts as chain transfer agent. Generally, the higherthe concentration of hydrogen employed, the lower the average molecularweight of the produced polymer.

The use of hydrogen gas as a means of controlling the average molecularweight of the polymer or copolymer applies generally to thepolymerisation process of the present invention. For example, hydrogencan be used to reduce the average molecular weight of polymers orcopolymers prepared using gas phase, slurry phase or solution phasepolymerisation conditions. The quantity of hydrogen gas to be employedto give the desired average molecular weight can be determined by simple“trial and error” polymerisation tests.

The polymerisation process of the present invention provides polymersand copolymers, especially ethylene polymers, at remarkably highproductivity (based on the amount of polymer or copolymer produced perunit weight of nitrogen containing transition metal complex employed inthe catalyst system). This means that relatively very small quantitiesof catalyst are consumed in commercial processes using the process ofthe present invention. It also means that when the polymerisationprocess of the present invention is operated under polymer recoveryconditions that do not employ a catalyst separation step, thus leavingthe catalyst, or residues thereof, in the polymer (eg as occurs in mostcommercial slurry and gas phase polymerisation processes), the amountcatalyst in the produced polymer can be very small. Experiments carriedout with the catalyst of the present invention show that, for example,polymerisation of ethylene under slurry polymerisation conditions canprovide a particulate polyethylene product containing catalyst sodiluted by the produced polyethylene that the concentration oftransition metal therein falls to, for example, 1 ppm or less wherein“ppm” is defined as parts by weight of transition metal per millionparts by weight of polymer. Thus polyethylene produced within apolymerisation reactor by the process of the present invention maycontain catalyst diluted with the polyethylene to such an extent thatthe transition metal content thereof is, for example, in the range of1–0.0001 ppm, preferably 1–0.001 ppm. Using a catalyst comprising anitrogen-containing Fe complex in accordance with the present inventionin, for example, a slurry polymerisation, it is possible to obtainpolyethylene powder wherein the Fe concentration is, for example, 1.03to 0.11 parts by weight of Fe per million parts by weight ofpolyethylene.

Methods for operating gas phase polymerisation processes are well knownin the art. Such methods generally involve agitating (e.g. by stirring,vibrating or fluidising) a bed of catalyst, or a bed of the targetpolymer (i.e. polymer having the same or similar physical properties tothat which it is desired to make in the polymerisation process)containing a catalyst, and feeding thereto a stream of monomer at leastpartially in the gaseous phase, under conditions such that at least partof the monomer polymerises in contact with the catalyst in the bed. Thebed is generally cooled by the addition of cool gas (eg recycled gaseousmonomer) and/or volatile liquid (eg a volatile inert hydrocarbon, orgaseous monomer which has been condensed to form a liquid). The polymerproduced in, and isolated from, gas phase processes forms directly asolid in the polymerisation zone and is free from, or substantially freefrom liquid. As is well known to those skilled in the art, if any liquidis allowed to enter the polymerisation zone of a gas phasepolymerisation process the quantity of liquid is small in relation tothe quantity of polymer present in the polymerisation zone. This is incontrast to “solution phase” processes wherein the polymer is formeddissolved in a solvent, and “slurry phase” processes wherein the polymerforms as a suspension in a liquid diluent.

The gas phase process can be operated under batch, semi-batch, orso-called “continuous” conditions. It is preferred to operate underconditions such that monomer is continuously recycled to an agitatedpolymerisation zone containing polymerisation catalyst, make-up monomerbeing provided to replace polymerised monomer, and continuously orintermittently withdrawing produced polymer from the polymerisation zoneat a rate comparable to the rate of formation of the polymer, freshcatalyst being added to the polymerisation zone to replace the catalystwithdrawn form the polymerisation zone with the produced polymer.

In the preferred embodiment of the gas phase polymerisation process ofthe present invention, the gas phase polymerisation conditions arepreferably gas phase fluidised bed polymerisation conditions.

Methods for operating gas phase fluidised bed processes for makingpolyethylene and ethylene copolymers are well known in the art. Theprocess can be operated, for example, in a vertical cylindrical reactorequipped with a perforated distribution plate to support the bed and todistribute the incoming fluidising gas stream through the bed. Thefluidising gas circulating through the bed serves to remove the heat ofpolymerisation from the bed and to supply monomer for polymerisation inthe bed. Thus the fluidising gas generally comprises the monomer(s)normally together with some inert gas (e.g. nitrogen) and optionallywith hydrogen as molecular weight modifier. The hot fluidising gasemerging from the top of the bed is led optionally through a velocityreduction zone (this can be a cylindrical portion of the reactor havinga wider diameter) and, if desired, a cyclone and or filters todisentrain fine solid particles from the gas stream. The hot gas is thenled to a heat exchanger to remove at least part of the heat ofpolymerisation. Catalyst is preferably fed continuously or at regularintervals to the bed. At start up of the process, the bed comprisesfluidisable polymer which is preferably similar to the target polymer.Polymer is produced continuously within the bed by the polymerisation ofthe monomer(s). Preferably means are provided to discharge polymer fromthe bed continuously or at regular intervals to maintain the fluidisedbed at the desired height. The process is generally operated atrelatively low pressure, for example, at 10 to 50 bars, and attemperatures for example, between 50 and 120° C. The temperature of thebed is maintained below the sintering temperature of the fluidisedpolymer to avoid problems of agglomeration.

In the gas phase fluidised bed process for polymerisation of olefins theheat evolved by the exothermic polymerisation reaction is normallyremoved from the polymerisation zone (ie, the fluidised bed) by means ofthe fluidising gas stream as described above. The hot reactor gasemerging from the top of the bed is led through one or more heatexchangers wherein the gas is cooled. The cooled reactor gas, togetherwith any make-up gas, is then recycled to the base of the bed. In thegas phase fluidised bed polymerisation process of the present inventionit is desirable to provide additional cooling of the bed (and therebyimprove the space time yield of the process) by feeding a volatileliquid to the bed under conditions such that the liquid evaporates inthe bed thereby absorbing additional heat of polymerisation from the bedby the “latent heat of evaporation” effect. When the hot recycle gasfrom the bed enters the heat exchanger, the volatile liquid can condenseout. In one embodiment of the present invention the volatile liquid isseparated from the recycle gas and reintroduced separately into the bed.Thus, for example, the volatile liquid can be separated and sprayed intothe bed. In another embodiment of the present invention the volatileliquid is recycled to the bed with the recycle gas. Thus the volatileliquid can be condensed from the fluidising gas stream emerging from thereactor and can be recycled to the bed with recycle gas, or can beseparated from the recycle gas and sprayed back into the bed.

The method of condensing liquid in the recycle gas stream and returningthe mixture of gas and entrained liquid to the bed is described inEP-A-0089691 and EP-A-0241947. It is preferred to reintroduce thecondensed liquid into the bed separate from the recycle gas using theprocess described in our U.S. Pat. No. 5,541,270, the teaching of whichis hereby incorporated into this specification.

When using the catalysts of the present invention under gas phasepolymerisation conditions, the catalyst, or one or more of thecomponents employed to form the catalyst can, for example, be introducedinto the polymerisation reaction zone in liquid form, for example, as asolution in an inert liquid diluent. Thus, for example, the transitionmetal component, or the activator component, or both of these componentscan be dissolved or slurried in a liquid diluent and fed to thepolymerisation zone. Under these circumstances it is preferred theliquid containing the component(s) is sprayed as fine droplets into thepolymerisation zone. The droplet diameter is preferably within the range1 to 1000 microns. EP-A-0593083, the teaching of which is herebyincorporated into this specification, discloses a process forintroducing a polymerisation catalyst into a gas phase polymerisation.The methods disclosed in EP-A-0593083 can be suitably employed in thepolymerisation process of the present invention if desired.

The present invention is illustrated in the following Examples.

EXAMPLES Example 9 9.1 Preparation of2.6-diacetylpyridinebis(2.4.6-trimethylanil)

To a solution of 2,6-diacetylpyridine (0.54 g; 3.31 mmol) in absoluteethanol (20 ml) was added 2,4,6-trimethylaniline (1.23 g; 2.5 eq.).After the addition of 2 drops of acetic acid (glacial) the solution wasrefluxed overnight. Upon cooling to room temperature the productcrystallised from ethanol. The product was filtered, washed with coldethanol and dried in a vacuum oven (50° C.) overnight. The yield was 60%of theoretical. ¹H NMR(CDCl₃): 8.50, 7.95, 6.94, (m, 7H, ArH, pyrH),2.33 (s, 6H, N═CCH₃), 2.28 (s, 6H, CCH₃), 2.05 (s, 12H, CCH₃). Massspectrum: m/z 397 [M]⁺.

9.2 Preparation of 2.6-diacetylpyridinebis(2.4.6-trimethylanil)FeCl₂

FeCl₂ (0.15 g; 1.18 mmol) was dissolved in hot n-butanol (20 ml) at 80°C. A suspension of 2,6-diacetylpyridinebis(2,4,6-trimethylaniline(0.5 g;1.18 mmol) in n-butanol was added dropwise at 80° C. The reactionmixture turned blue. After stirring at 80° C. for 15 minutes thereaction was allowed to cool down to room temperature. The reactionvolume was reduced to a few ml and diethyl ether was added toprecipitate the product as a blue powder, which was subsequently washedthree times with 10 ml diethyl ether. The yield was 64% of theoretical.

Mass spectrum: m/z 523 [M]⁺, 488 [M−Cl]⁺, 453 [M−Cl₂]⁺.

Example 27 (Comparative)

This Example shows polymerisation using a catalyst system containingonly a catalyst covered by the definition (1) in the present invention.

Preparation of the Supported Catalyst

2,6-diacetylpyridinebis(2,4,6-trimethylanil)FeCl₂ was prepared asdescribed in Example 9. Silica (1.38 g ES70, supplied by Crosfield),which had been heated under flowing nitrogen at 700° C., was placed in aSchlenk tube and toluene (10 ml) was added.

To a solution of 2,6-diacetylpyridinebis(2,4,6-trimethylanil)FeCl₂(0.041 g) in toluene (10 ml) was added methylaluminoxane (13.2 ml, 1.78Min toluene, supplied by Witco). This mixture was heated at 40° C. for 30minutes to dissolve as much of the iron complex as possible. Thesolution was then transferred to the silica/toluene. Thesilica/MAO/toluene mixture was maintained at 40° C., with regularstirring, for 30 minutes before the toluene was removed, at 40° C.,under vacuum to yield a free flowing powder. Analysis of the solid gave16.9% w/w Al and 0.144% w/w Fe.

Polymerisation Tests

The reagents used in the polymerisation tests were: hydrogen Grade 6.0(supplied by Air Products): ethylene Grade 3.5 (supplied by AirProducts): hexene (supplied by Aldrich) distilled over sodium/nitrogen:dried pentane (supplied by Aldrich): methylaluminium (2M in hexanes,supplied by Aldrich): and triisobutylaluminium (1M in hexanes, suppliedby Aldrich).

A 3 liter reactor was baked out under flowing nitrogen for at least 1hour at 77–85° C. before powdered sodium chloride (300 g, predried undervacuum, 160° C., >4 hours) was added. The sodium chloride was used as afluidisable/stirrable start-up charge powder for the gas phasepolymerisation. Trimethyl aluminium (3 ml, 2M in hexanes) was added tothe reactor and was boxed in nitrogen. The alkyl aluminium was allowedto scavenge for poisons in the reactor for between ½–1 hour before beingvented using 4×4 bar nitrogen purges. The gas phase composition to beused for the polymerisation was introduced into the reactor andpreheated to 77° C. prior to injection of the catalyst composition. Thecatalyst (0.18–0.22 g) was injected under nitrogen and the temperaturethen adjusted to 80° C. The ratio of hexene and/or hydrogen to ethyleneduring the polymerisation was kept constant by monitoring the gas phasecomposition by mass spectrometer and adjusting the balance as required.The polymerisation tests were allowed to continue for between 1 to 2hours before being terminated by purging the reactants from the reactorwith nitrogen and reducing the temperature to <30° C. The producedpolymer was washed with water to remove the sodium chloride, then withacidified methanol (50 ml HCl/2.5 L methanol) and finally withwater/ethanol (4:1 v/v). The polymer was dried under vacuum, at 40° C.,for 16 hours. All the polymerisation tests were carried out at apolymerisation temperature of 80° C. and at an ethylene pressure of 8bars. The polymerisation conditions are set out in the following Table.

TABLE 1 Other cocatalyst Temp Ethylene H₂ hexene SCB/ Ex. mmols ° C.barg barg barg 1000 C 27.3 TMA^(#)/6 80 8 0.5 0.2 0.1 27.7 — 80 8 — 0.861.6 ^(#)2M Solution of trimethylaluminium in toluene (supplied byAldrich)

These results show the relatively low level of comonomer incorporationwhen only a single Fe based catalyst is used; the higher level inExample 27.7 required a much greater amount of hexene to be added.

Example 32 32.1—Preparation of a Supported Ziegler Catalyst Component

Silica (20 kg), grade ES 70 supplied by Crosfield, which had been driedat 800° C. for 5 hours in flowing nitrogen, was slurried in hexane (110liters) and hexamethyldisilazane (30 moles), supplied by Fluka, wasadded with stirring at 50° C. Dry hexane (120 liters) was added withstirring, the solid allowed to settle, the supernatant liquid removed bydecantation and further dry hexane (130 liters) was added with stirring.The hexane washing was repeated a further 3 times. Dibutylmagnesium (30moles), supplied by FMC, was added and stirred for 1 hour at 50° C.Tertiary butyl chloride (60 moles) was added and stirred for 1 hour at50° C. To this slurry was added an equimolar mixture of titaniumtetrachloride (3 moles), and titanium tetra-n-propoxide (3 moles) withstirring at 50° C. for 2 hours, followed by 5 washings with dry hexane(130 liters). The slurry was dried under a flowing nitrogen stream togive a solid, silica supported Ziegler catalyst component.

32.2—Preparation of a Mixed Catalyst by Coimpregnation Containing aZiegler Component and the Catalyst of Example 9

A solution of methylaluminoxane (“MAO”, 10.2 mmol) as a 10% wt solutionin toluene, supplied by Witco, was added to a suspension of2,6-diacetylpyridinebis(2,4,6-trimethylanil)FeCl₂ (0.07 mmol in 5 ml drytoluene), prepared as in Example 9, and the mixture shaken for 5minutes. This solution was then added to 2.0 g of the silica supportedZiegler catalyst prepared above (Example 32.1), the mixture shaken for 2hours at 20° C. and then the solvent removed under reduced pressure at20° C. to yield the mixed catalyst as a free flowing powder.

32.3–32.4—Preparation of Mixed Catalysts by Sequential ImpregnationContaining a Ziegler Component and the Catalyst of Example 9

A sample of silica supported Ziegler catalyst (as prepared in 32.1above) was placed in a schlenk tube and toluene (5 ml) added to form aslurry. Methylaluminoxane, MAO (1.78M in toluene, supplied by Witco) wasadded to the schlenk and the resultant slurry shaken intermittently atroom temperature for 30 minutes. The supernatant liquid was removed andthe solid washed with toluene (10 ml) at room temperature. The volatilecomponents of the resultant solid were then removed under reducedpressure at 20° C. to yield a solid free flowing powder.

(2,6-diacetylpyridinebis(2,4,6 trimethyl anil) iron dichloride (preparedas described in Example 9 above) was added to a slurry of the abovepowder in toluene (10 ml) at room temperature for 1 hour. The mixturewas occasionally shaken then the supernatant was removed by decantationand the resulting solid was dried under vacuum at 20° C.

Two catalysts were made by this method, with the amounts of eachcatalyst component (“Ziegler” and “Fe”) and MAO used given below:

Fe MAO Ziegler/MAO Ziegler/MAO/Fe Catalyst Ziegler g mmol mmol washing(toluene) washing (hexane) 32.3 2 0.070 10.45 1 × 10 ml 2 × 5 ml 32.4 20.073 3.56 1 × 10 ml 2 × 5 ml

32.5–32.18—Polymerisation of ethylene/hexene mixture using a mixedcatalyst

A 3 liter reactor equipped with a helical stirrer was heated to 77–95°C. for 1 hour with dry nitrogen flowing through. Dry sodium chloride(300 g) was then added with trimethylaluminium (TMA) solution (2 ml of 2molar TMA in hexane) and the reactor heated at 85° C. for 0.5–1 hours.The reactor was purged with nitrogen, cooled to 50° C. and TMA solution(3 ml of 2 molar TMA in hexane) added. The temperature was raised to 77°C. and hydrogen (0.5 bar) and ethylene (8 bar) added prior to theaddition of 1-hexene (2.6 ml). Reaction was started by injection intothe reactor of one of the mixed catalysts 32.2, 32.3 or 32.4 (0.1–0.3 g)prepared above. The temperature was maintained at 80° C. and ethyleneadded to maintain constant pressure. The gas phase was monitored by amass spectrometer and hydrogen and 1-hexene added as necessary tomaintain constant gas phase concentrations of these components. Thepolymerisation was carried out for 60 minutes. The polymer was washedwith water to remove the sodium chloride, then with acidified methanol(50 ml HCVI/2.5 liters methanol) and finally with water/ethanol (4:1v/v). The polymer was dried under vacuum, at 40° C. for 16 hours.

Details of the reactions are given in Table 2 below. For Examples 32.3to 32.8, 32.10, 32.11 and 32.13, R=0.025 and 18.18R−0.16=0.29. ForExample 32.9, R=0.050 and 18.18R−0.16=0.75. For Example 32.12, R=0.038and 18.18R−0.16=0.51.

TABLE 2 Gas phase Catalyst Catalyst co-catalyst/ Temp Ethylene H₂1-hexene Polymer SCB/ Ex. used Injected g mmols ° C. barg barg bargYield g 1000 C 32.5 32.3 0.19 TMA^(#)/20 80 8 0.08 0.2 68 5.7 32.6 32.30.19 TMA^(#)/6 80 8 0.09 0.2 161 1.4 32.7 32.3 0.18 TMA^(#)/20 80 8 0.50.2 55 3.7 32.8 32.3 0.18 TMA^(#)/6 95 8 0.5 0.2 156 2.6 32.9 32.3 0.19TEA*/6 80 8 0.5 0.2 143 0.4 32.10 32.3 0.18 TMA^(#)/12 80 8 0.5 0.2 662.5 32.11 32.3 0.10 TMA^(#)/6 80 8 0.5 0.4 59 6.6 32.12 32.3 0.19TMA^(#)/6 80 8 0.5 0.2 123 1.8 32.13 32.3 0.12 TMA^(#)/6 65 8 0.28 0.284 32.14 32.3 0.10 TMA^(#)/6 80 14 0.17 0.3 185 32.15 32.4 0.12TMA^(#)/6 80 8 0.5 0.2 82 32.16 32.2 0.20 TMA^(#)/6 80 8 0.5 0.2 111 2.332.17 32.2 0.21 TMA^(#)/6 80 8 3 0.2 55 3.5 32.18 32.2 0.20 TMA^(#)/6 808 0.06 0.2 76 3.2 ^(#)2M Solution of trimethylaluminium in toluene(supplied by Aldrich) *1M Solution of triethylaluminium in hexanes(supplied by Aldrich)

The above table shows clearly that much higher levels of comonomerincorporation are achieved at relatively low levels of comonomerconcentration by the used of the mixed catalyst system of the invention(compare Example 27.3, which also has a hexene partial pressure of 0.2bar but an SCB of only 0.1/1000 C). The comonomer incorporation is alsoconcentrated in the high molecular weight part of the copolymer.

Physical Properties of Product of Example 32.5

Modulus Measurement

Modulus test samples were compression moulded to a thickness ofapproximately 200 mm using a Moores hydraulic press. A picture framemould was prepared by cutting a 25 cm square in a sheet of aluminiumfoil and sandwiching this frame between two sheets of melinex, aluminiumsheet, and steel plates. 3 g of polymer was evenly arranged in thepicture frame mould, which was then assembled and transferred to thepress (pre-heated to 200° C.). The plattens were then closed to acontact pressure of 10 kg/cm² and held for 3 minutes after which fullpressure (20 tons) was applied for 5 minutes. The press was then crashcooled with cold water running through the plattens with the pressureheld at 20 tons. Once cool the pressure was released, moulddisassembled, and the flash trimmed from the polymer sheet. For modulusmeasurement parallel sided specimens of dimensions 100 mm×5 mm were cutfrom each sheet and the exact dimensions accurately measured.

Samples were tested in an Instron using a 100N load cell at a strainrate of 2 mm/min. Samples were gripped with a pneumatic grip at thebottom and a manual screw grip at the the top so that the guage length(ungripped section) of the sample was 20 mm. The 1% secant modulus wascalculated over the initial (1% strain) linear section of thestress-strain curve. Typically six specimens were tested and the resultsaveraged.

The product of Example 32.5 was found to have a secant modulus of 529MPa. It had an SCB of 5.7/1000 C. This values are plotted in FIG. 1 (thesingle point above the diagonal line), together with pointscorresponding to commercially available copolymers outside the scope ofthe invention.

The polymer of Example 32.5 had a broad molecular weight distribution(as determined by gel permeation chromatography. The polydispersity(Mw/Mn) was 28.5.

Dynamic Shear Rheometry Measurement

2 g of polymer sample (containing 0.2% Irganox 1010 antioxidant ifuncompounded reactor powder used) was weighed out and distributed evenlyaround a steel mould shaped in form of disks 25 mm diameter and 2 mm inthickness. This mould was sandwiched between steel plates and placed ina press pre-heated to 190° C. The sample was exposed firstly to lowpressure (10 kg/cm²) for 3 mins then high pressure (20 tons) for 5 mins,after which the press plattens were rapidly cooled via a supply of coldwater. Once the plattens had reached room temperature the pressure wasreleased and sample removed. Excess polymer flashing was removed priorto loading into the rheometer.

Sample rheology was measured with a Rheometrics RDS2 dynamic,strain-controlled rheometer at 180° C. using a strain of 5%, parallelplate geometry (25 mm diameter plates), over a frequency range of0.01–100 rad/s.

A plot showing the complex viscosity of Example 32.3 compared with twocommercial HDPE tough film grades is shown in FIG. 2; this demonstratesthat the copolymer has acceptable Theological properties for commercialuse.

Holtrop Analysis of the Polymer Produced in Example 32.5

Mixtures of 2-n-butoxyethanol, xylene and Irganox 1010 Ffat (0.15 g)were premeasured into round bottom flasks. Fraction 1 (see Table 3abelow) was placed in a cruicible and heated to 120–122° C. A sample ofpolymer (5 g) was ground using a Reich mill (1 mm mesh) and added to thepre-heated solvent mixture. The polymer slurry was stirred 60 rpm for 20minutes after which the liquid components of the mixture were drainedthrough a microfilter, cooled and mixed with acetone (500 ml) in orderto precipitate the dissolved polymer. The next solvent fraction was thenadded to the crucible and the procedure repeated in order for all thesolvent ratios shown below. The isolated polymers were dried for 6 hoursin a vacuum oven at 40° C. prior to analysis.

TABLE 3a Non-solvent Solvent FRACTION 2-n-butoxyethanol (ml) Xylene (ml)TOTAL (ml) 1 186 114 300 2 174 126 300 3 162 138 300 4 156 144 300 5 150150 300 6 146 154 300 7 142 158 300 8 138 162 300 9  0 300 300 1254 1446  2700 

TABLE 3b Mw Mn SCB/1000 C SCB/1000 C Fraction (× 10³) (× 10³) Mw/Mn IR¹H NMR Bulk 304 20 15 6.5 5.8 1 8.3 2.21 3.76 1.3 3.8 2 21.3 6.16 3.465.9 4.9 3 41.5 13.2 3.14 6.3 4 79.1 31.6 2.5 9 6.8 5 121.4 32.2 3.77 7.86 109.2 38.9 2.81 7.2 7 132.1 46.2 2.86 6.3 8 318 36.4 4.8 9 582.3 127.64.56 3.3

These results show that for a product derived from a multisite catalystand being at the very earliest experimental stage (and thereforenon-optimised), comonomer can be preferentially incorporated in afraction of the copolymer with respect to product molecular weight.

Example 41

Example shows the use of a combination of a metallocene-type catalystwith a catalyst based on an iron complex of the present invention forpolymerising ethylene under slurry conditions.

41.1—Preparation of a Supported Metallocene Catalyst

To silica (Crosfield grade ES70, previously calcined at 200° C. inflowing N₂ for 5 hrs) was added a toluene solution of methylaluminoxane(MAO) containing dissolved bis(n-butylcyclopentadienyl)ZrCl₂. Theamounts used were 2.5 mmol MAO per gram of silica and 0.05 mmolmetallocene per gram silica. The resulting slurry was stirred gently forat least 1 hour before being dried under reduced pressure to give a freeflowing powder.

41.2—Preparation of the Combined Metallocene/Fe-complex Catalyst

The supported metallocene catalyst (2.5 g) prepared as described in step41.1 above was placed in a Schlenk tube and a slurry of2,6-diacetylpyridinebis(2,4,6 trimethyl anil) iron dichloride (73 mg) inhexane (10 ml) was added thereto at ambient temperature. The mixture washeated to 80° C. and left for 90 minutes with occasional shaking tomaintain a well-mixed solution. There was no colouration evident in thesupernatant solution above the solid. The produced catalyst was dried at80° C. under vacuum to leave a dry free flowing powder.

41.3—Polymerisation of Ethylene

A 1 liter reactor was heated under flowing nitrogen for 1 hour at 80° C.before being cooled to 30° C. Triisobutyl aluminium (3 ml of 1M inhexanes) was added to the reactor followed by 500 ml of isobutane. Thereactor was heated to 77° C. and the pressure increased to 12.9 bar.Ethylene was added to give 20.9 bar total pressure. The catalyst (0.100g, slurried in hexane) prepared as described in 41.2 above was injectedinto the reactor. The ethylene pressure during the polymerisation wasestimated to be approximately 8 bar. Polymerisation was allowed tocontinue for 60 minutes. 96 g of polymer was recovered. Analysis of thepolymer by GPC indicated Mw and Mn to be 471000 and 30000 respectively.

Comparative Test 41.4

This shows the polymerisation of ethylene using only the supportedmetallocene catalyst described in step 41.1.

A 1 liter reactor was heated under flowing nitrogen for 1 hour at 80° C.before being cooled to 30° C. Triisobutyl aluminium (3 ml of 1M inhexanes) was added to the reactor followed by 500 ml of isobutane. Thereactor was heated to 75° C. and the pressure increased to 12.7 bar.Ethylene was added to give 20.7 bar total pressure. The supportedmetallocene catalyst (0.094 g, slurried in hexane) prepared in step 41.1above was injected into the reactor. The ethylene pressure during thepolymerisation was estimated to be approximately 8 bar. Polymerisationwas allowed to continue for 60 minutes. 49 g of polymer was recovered.Analysis of the polymer by GPC indicated Mw and Mn to be 142000 and53000 respectively.

Example 42

This Example shows the use of a combination of a Phillips catalyst witha catalyst based on an iron complex of the present invention forpolymerising ethylene under slurry conditions.

42.1 Preparation of Phillips Catalyst

To HA30WFL Phillips Cr on silica catalyst (Supplied by Grace, activatedin flowing air for 5 hrs at 550° C., 295.1 g) was added a toluenesolution of MAO (Witco, 515 ml×1.47 M, 0.76 mol). The addition took 30minutes during which time the flask was gently swirled to ensure an evencoating and the orange Cr catalyst turned chocolate brown. The slurrywas placed in a waterbath at 50° C. for 1 hr and was shaken periodicallyto thoroughly mix. The solvent was then removed by vacuum at 50° C.until fluidisation of the catalyst had stopped, leaving a free flowingkhaki-green powder. Yield=347.7 g. Analysis by ICP 5.96w/w % Al and0.85w/w % Cr.

42.2 Preparation of mixedPhillips/2,6-diacetylpyridinebis(2.4.6-trimethylanil)FeCl₂ catalyst

To the MAO treated Phillips catalyst of Example 42.1 (2.7 g) slurried inanhydrous hexane (10 ml) was added a slurry of2,6-diacetylpyridinebis(2,4,6 trimethyl anil) iron dichloride fromExample 9.2 (36 mg, 6.9×10⁻² mmol) in anhydrous hexane (10 ml). Theresulting slurry was vigorously shaken for 10 mins, the solid allowed tosettle and the colourless supernatant decanted. The remaining solid waswashed with hot hexane (2×15 ml), decanted and pumped dry under vacuumat 50° C. until fluidisation of the solid had stopped yielding agreen/brown free flowing powder. Iron loading calculated to be 0.14%w/w.

42.3—Polymerisation of Ethylene

A 1 L reactor was heated under flowing nitrogen for 1 hour at 90° C.before being cooled to 30° C. Triisobutyl aluminium (3 ml×1M in hexanes)followed by isobutane (500 ml) was added to the reactor. The reactor wassealed and heated to 80° C. raising the pressure to 13.9 bar. Ethylenewas added to give 26.9 bar total pressure, the vessel was again sealedand cooled to 78° C. The catalyst of Example 42.2 (0.099 g, slurried in5 cm³ hexane) was injected into the reactor raising the pressure by 0.3bar. The reactor pressure was controlled at 27.2 bar during the test(ethylene pressure estimated to be approximately 13.0 bar) and thetemperature adjusted to 80° C. Polymerisation was allowed to continuefor 120 minutes. 76.1 g of polymer was recovered. Analysis of thepolymer by GPC indicated Mw and Mn to be 722000 and 15000 respectively(polydispersity=48.0).

Example 45

This Example shows the preparation of a further mixed catalystcomprising a Ziegler catalyst and the catalyst prepared in Example 9above. The polymer made using this catalyst was blown into a film.

Pre-Impregnation of Support with Activator Compound

All the following operations were conducted under a nitrogen atmosphereunless stated. A sample of silica supported Ziegler catalyst was placedin a schlenk tube and toluene added to form a slurry. Methylaluminoxane,MAO (1.78M in toluene, supplied by Witco) was added to the schlenk tubeand the resultant slurry mixed intermittently at room temperature. Thesupernatant liquid above the solid was removed and the solid washed withtoluene at room temperature. The volatile components of the resultantmaterial were then removed under reduced pressure at 20° C. to yield thesolid as a free flowing powder. Four different supports were prepared,listed in Table 4 below.

TABLE 4 Silica Toluene in Reaction Toluene Ex- supported MAO MAO:Tislurry time wash ample Ziegler g mmol ratio cm³ mins cm³ 45.1 20 10425:1  50 30 100 45.2 50 261 25:1 125 30 125 45.3 80 418 25:1 100 60 10045.4 80 167 . . . 300 30 200Supporting the Catalyst

2,6-diacetylpyridinebis(2,4,6 trimethyl anil) iron dichloride preparedas described in Example 9 above was added to a slurry of each of thefour the solid supports in toluene at room temperature. The mixture wasoccasionally shaken, the supernatant solution removed, and the supportedcatalyst washed with toluene followed by a mixture of hexanes (hexane40–60° C., supplied by Aldrich). The solid was dried under vacuum at 20°C. Table 5 below shows the preparative details for the four catalyststhus prepared.

TABLE 5 Toluene Re- Sup- in action Toluene Hexane Ex- port Fe MAO:Feslurry time wash wash ample g mmol ratio cm³ mins cm³ cm³ 45.1 26 0.70150:1   100 45 0 100 45.2 30 0.70 100:1** 100 45 0 100 45.3 105 2.79150:1   400 30 400 400 45.4 90 1.11 150:1   220 30 150 140

Preparation of Mixed Catalysts by Coimpregnation Containing a ZieglerComponent and the Catalyst of Example 9

All the following operations were conducted under a nitrogen atmosphereunless stated. A solution of methylaluminoxane as a 10% wt solution intoluene, supplied by Witco, was added to a suspension of2,6-diacetylpyridinebis(2,4,6-trimethylanil)FeCl₂, prepared as inExample 9, and the mixture shaken. This solution was then added to thesilica supported Ziegler catalyst prepared above (Example 32.1) and theresultant slurry mixed intermittently at room temperature. The volatilecomponents of the resultant material were then removed under reducedpressure at 20° C. to yield the mixed catalyst as a free flowing powder.The supported catalysts prepared, are listed below.

Silica Toluene Reaction Supported MAO Fe in slurry time Example Zieglerg mmol mmol MAO:Ti:Fe cm³ mins 45.5 200 348 8.40 41:5:1 400 30 45.6 100139 1.68 83:12:1 200 30Polymerisation

The six catalysts prepared above were used to polymerise ethylene. Thepolymerisation was conducted in a continuous fluidised bed reactor of 15cm diameter.

Ethylene, n-hexene, hydrogen and TEA/TMA were fed into the reactor:starting with a seed-bed of polyethylene powder (approx. 1000 g),catalyst was injected into the reactor and the polymerisation carriedout to increase the mass of the bed to approximately 3.5 kg.Polymerisation and product withdrawal was continued to yield a productsubstantially free of the starting bed. Process conditions for each ofthe polymerisations conducted are given in Table 6 below.

TABLE 6 Ti Si Aluminium Ethylene Hexene Al residue residue residueExample Alkyl H₂ [bar] [bar] [bar] ppm ppm ppm 45.1 TEA 0.46 8 0.18 934.4 180 45.2a TEA 0.23 4 0.09 94 4.9 160 45.2b TEA 0.16 4 0.09 72 6 22245.3 TEA 0.17 4 0.09 175 4.2 160 45.4 TEA 0.17 4 0.09 146 6.7 193 45.5aTMA 0.26 4 0.20 208 6.2 152 45.5b TMA 1.68 8 0.00 174 7.5 216 45.6 TEA0.49 4 0.2 185 9.9 285Properties of the polymers obtained for the above polymerisations aregiven in Table 7 below, with additional data for Examples 45.5a and45.5b in Table 8.

TABLE 7 Average Example HLMI HLMI Density kg/m³ Mn Mw Mw/Mn Bu/1000 C45.1  3.5 3.5 945 — — — 1.6 45.2a 5.2–4.2 4.5 952 15000 268000 18.4 0.745.2b 3.3–3.8 4 951 19000 278000 14.4 45.3 2.98–3.7  3 951 19000 24100012.4 45.4 3.38–4   3.5 948 27000 245000 9.2 45.5a 10.5 10.5 951 23000165000 7.1 45.5b 10.5 10.5 957 22000 234000 10.8 45.6 11.5 11.5 95026000 168000 6.4

TABLE 8 Average PE Yield Particle % Fines Example KgPE/gCatalyst Size(μm) (<125 μm) Span 45.5a 2.2 458 2.6 1.3 45.5b 1.6 350 8.2 1.6Compounding

The polymers in Table 6 were compounded: the powder extracted from thepolymerisation reactor was stabilised with 1000 ppm of processantioxidant Irgafos PEPQ, 1000 ppm of a long term antioxidant Irganox1010 and 1000 ppm of a neutralizer (calcium stearate). The blend ofpowder and additives was compounded in a twin screw extruder type Werner53 equipped with two 53 mm diameter screws with a length/diameter ratioof 48. The temperature profile along the screw was between 220° C. and240° C.

Film Blowing

The compounded polymers 45.1 to 45.4 were then extruded on an AXON BX18type extruder with a die diameter of 70 mm, and a die gap of 1 mm. Thescrew diameter was 18 mm with a LID ratio of 30. Details of theextrusion conditions are given in Table 9 below, together with the FilmAppearance Rating (FAR), which is a measurement of the gels andfish-eyes content in each film sample.

TABLE 9 Example 45.1 45.2a 45.2b 45.3 45.4 Temp profile (° C.) 190–230190–230 190–130 190–230 190–230 Screw speed (revs/min) 154 148 196 170150 Melt pressure (bar) 428 468 495 497 488 Melt temp (° C.) 221 222 223229 226 Output (kg/hr) 1.5 1.9 2.0 2.2 2.0 Take off speed (m/min) 2.12.5 3.0 2.5 2.5 Blow Up Ratio 2:1 2:1 2–3:1 2:1 2:1 Frostline (mm) min*min min min min Motor load (Amps) 3.10 3.06 3.0 2.97 3.19 Film thickness(μm) 12.32 22.30 18–26 25–32 22–26 FAR −40 −40 −20 −30 −20 *minimumfrostline means that the change from molten to solid film occurred atthe minimum distance from the air ring blowing the film.The compounded polymers 45.5 a, 45.5 b and 45.6 were extruded on aCollin type extruder with a die diameter of 70 mm, and a die gap of 0.8mm. Details of the extrusion conditions are given in Table 10 below,together with the Film Appearance Rating (FAR).

TABLE 10 Example 45.5a 45.5b 45.6 Screw speed (revs/min) 38 38 37 Meltpressure (bar) 460 430 417 Melt temp (° C.) 181 177 180 Output (kg/hr) 99 9 Take off speed (m/min) 14.4 14.4 14.2 Blow Up Ratio 3:1 3:1 3:1Motor load (Amps) 16.9 15.5 15.6 Film thickness (μm) 17–22 16–20 14–22FAR +20 +20 +20These results show that for a product derived from a multisite catalystand being at the very earliest experimental stage (and thereforenon-optimised), the optical properties are surprisingly good. Therelatively good film appearance rating FAR indicates that there areunexpectedly low gel levels in the film.

1. Copolymer of ethylene and a further 1-olefin wherein the degree ofshort chain branching per thousand carbons (SCB) is from 2.0 to 10, andthe relationship of modulus in MPa (M) to SCB (B) is defined by theequation M=k−62.5B where k is 820 or greater.
 2. Copolymer according toclaim 1 wherein the SCB is between 2 and
 8. 3. Copolymer according toclaim 1 wherein the SCB is greater than 2.5.
 4. Copolymer according toclaim 1 wherein k is 830 or greater.
 5. Copolymer according to claim 3wherein SCB is greater than 3.0.
 6. Copolymer according to claim 4wherein k is 840 or greater.
 7. Copolymer according to claim 6 wherein kis 850 or greater.